Integrated circuit devices, such as semiconductor chips, are commonly packaged using a lead frame and encapsulant material, such as a molding compound. For example, one or more semiconductor chips may be physically attached and electrically connected to a lead frame. The encapsulant material is formed around the semiconductor chip and electrical connections. The encapsulant protects the semiconductor chip and electrical connections from damaging environmental conditions, such as moisture, temperature, foreign particles, etc. The leads of the lead frame are externally accessible from outside of the encapsulant, and in some cases protrude away from the encapsulant. These outer portions of the leads provide external electrical terminals that allow the packaged device to be electrically connected to a printed circuit board, for example.
Many semiconductor processing technologies utilize lead frame strips to simultaneously package a number of semiconductor devices. A lead frame strip includes a number of unit lead frames continuously repeated on a sheet conductor, with openings in the sheet conductor defining the features of the unit lead frames. Each unit lead frame provides the lead construction for a single packaged device. One or more semiconductor dies can be affixed to and electrically connected with each unit lead frame. Eventually, the unit lead frames are singulated from one another to form individual packaged devices. The encapsulant may be molded on the lead frame before or after the unit lead frames are singulated.
In semiconductor packaging, delamination is a common problem in which the packaging material separates from the lead frame due to poor adhesion between the two. This may present an unacceptable risk that moisture and foreign particles will penetrate the package, and may result in a number of parts being discarded after inspection.
One technique for addressing the adhesion problem involves the application of an adhesion promoter to the lead frame prior to forming the encapsulant on the lead frame. However, effective adhesion promoters are typically non-conducting or at least interfere with conductive connections. Therefore, if the adhesion promoter is not removed from certain regions of the lead frame prior to wire bonding, there is a substantial possibility of wire bond failure. Known techniques for removing adhesion promotors from certain regions of the lead frame require multiple process steps that are costly and difficult to calibrate.